[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: 19990716: gempak/garp <fwd>

Dear Steve,

Right.  When PVOR ingests THTA instead of TMPK, 
everything's fine and there's no sign or order-of-mag 
problem.  The built-in use of TMPK is what threw me.

John

On Thu, 15 Jul 1999 15:56:57 -0600 Steve Chiswell 
<address@hidden> wrote:

> 
> 
> 
> John,
> 
> I looked at the DV_PVOR code I mentioned the other day, and
> verified that the PVOR formula includes the -g term.
> 
> As you mention below, the PVOR equation can accept either
> THTA/THTE/STHA when the layer is pressure and tmperature when
> operating in isentropic coordinates.
> 
> I plotted a cross section of today's eta using PVOR(THTA,WND)
> and the PV values are on the order of 1.2 to 1.6 around 300 mb and
> increasing rapidly above this. 
> 
> Steve Chiswell
> Unidata User Support
> 
> 
> 
> On Thu, 15 Jul 1999, John Knox wrote:
> 
> > Dear Steve,
> > 
> > Here's the problem. {See e-mail appended below.}  I 
> > cross-verified this fix by using someone else's code who 
> > also used thta, not tmpk, and it works.  I should have 
> > checked the variable definition more carefully... I saw 
> > "TMPK" and because theta (potential temperature) is always 
> > in degrees K, it didn't occur to me that that wasn't 
> > potential temperature.  This would completely explain the 
> > not-quite-order-of-magnitude differences.
> > 
> > John
> > 
> > 
> > --- Begin Forwarded Message ---
> > Date: Thu, 15 Jul 1999 14:31:10 -0700 (PDT)
> > From: Lynn McMurdie <address@hidden>
> > Subject: gempak/garp
> > Sender: Lynn McMurdie <address@hidden>
> > To: address@hidden
> > 
> > Reply-To: Lynn McMurdie <address@hidden>
> > Message-ID: 
> > <address@hidden>
> > 
> > 
> > Hi John...
> > 
> > In the cross-section part of garp, select PotVort_Ks-1P-1 and change
> > the line below FROM:
> > 
> > PVOR (TMPK,WND)
> > 
> > to PVOR (THTA,WND).
> > 
> > Potential vorticity should be in terms of theta.  You could still
> > divide by gravity, but maybe it shouldn't be negative gravity.  Don't
> > have the time to ponder the units at this moment, but give that a try
> > and see if the magnitudes look better.
> > 
> > Good luck....garp is SO MUCH fun!!!
> > 
> > Cheers,
> >     Lynn
> > -- 
> > Lynn McMurdie               INTERNET: address@hidden
> > (206) 685-9405              UUCP:     
> > uw-beaver!atmos.washington.edu!mcmurdie
> > Dept of Atmospheric Sciences
> > University of Washington
> > Box 351640
> > Seattle, WA  98195
> > --- End Forwarded Message ---
> > 
> > 
> > ------------------------------------------------
> > Dr. John A. Knox
> > Assistant Professor of Geography and Meteorology
> > Room 15, Mueller Hall
> > Valparaiso University
> > Valparaiso, IN 46383
> > E-mail: address@hidden
> > Office Phone: 219-464-6003
> > 
> > 
> 

------------------------------------------------
Dr. John A. Knox
Assistant Professor of Geography and Meteorology
Room 15, Mueller Hall
Valparaiso University
Valparaiso, IN 46383
E-mail: address@hidden
Office Phone: 219-464-6003